The present invention relates to a low-inductive busbar arrangement for a three-point phase module of a polyphase three-point power converter, and to a low-inductive busbar arrangement of said three-point power converter.
In power converters which use fast-switching turn-off power semiconductor switches, for example Insulated Gate Bipolar Transistor (IGBT), care should be taken to ensure that the value of the leakage inductance of the connections between these turn-off power semiconductor switches and the intermediate circuit capacitors is minimized. This limits the voltage spikes both during turn-on and during turn-off of the power semiconductor switches, in order to avoid relatively high loading or even destruction of the power semiconductor switches. In order to minimize the leakage inductance, the connections and the leads are embodied as a busbar arrangement.
A low-inductive busbar arrangement for a two-point power converter having fast-switching turn-off power semiconductor switches has two busbars which are routed in a plane-parallel manner and are electrically insulated from one another by means of an insulating layer. The current in these two busbars must flow in opposite directions to ensure that the leakage inductance of this busbar arrangement becomes minimal. Appropriately configured copper plates are generally used as busbars. The distance between the two busbars is determined by the insulating layer, the thickness thereof being dependent on the voltage load. The areas of the busbars which overlap in the current path should be maximal, the overall construction of the power converter forming a natural limit to this. Various design proposals for a two-point inverter were presented by Dr. Schutze on Mar. 9, 1997 at the World Sales Meeting of the firm eupec.
In the paper xe2x80x9cIGBT-Wechselrichter fur Antriebe in Industrie und Verkehrxe2x80x9d [IGBT inverters for drives in industry and transport] by Dr. Salama and Dr. Tadros, printed in ETG-Fachbericht 39 (papers of the ETG specialist conference on May 13 and 14, 1992 in Bad Nauheim), pages 281 to 295, a multilayer technology having all connections and leads within the power section is used as low-inductive busbar arrangement of an IGBT three-point inverter. In accordance with FIG. 4 of this specialist paper, this involves a five-layer conductor routing. A multilayer of this type is compact and, at the same time, is a support plate for snuffer and/or intermediate circuit capacitors and for the drive units of the individual fast-switching turn-off power semiconductor switches. Depending on the DC input voltage used for the IGBT inverter, the number of layers of the multilayer increases, and thus so, too, does the outlay for creating such a multilayer. A further significant disadvantage of this busbar arrangement technology resides in the costs of the multilayer.
In the event of a fault, for example a defect on one of the twelve IGBTs or on one of the 14 diodes, the outlay for exchanging an IGBT or a diode is very costly since the entire three-point inverter has to be disassembled. A further disadvantage of this multilayer is that if a line break occurs in one conductor plane, the entire multilayer must be exchanged for a new one. This operation is also labor-intensive and time-consuming. Moreover, a fabricated multilayer can only be used for one embodiment of an IGBT inverter. If, for a switch of the three-point inverter, not one IGBT but two or three IGBTs which are electrically connected in series are intended to be used owing to the higher DC input voltage, then it is necessary to develop a completely new multilayer in which at least the number of conductor planes is likewise increased. In other words, different multilayers are required for a three-point inverter with the series connection number One, Two or Three.
The present invention is based on the object of specifying a low-inductive busbar arrangement for a three-point phase module of a polyphase three-point power converter which has a small number of layers and can be expanded in a simple manner.
By virtue of the fact that the individual different busbars of a three-point phase module are divided between three busbar planes of the inductive busbar arrangement, which are mutually electrically insulated from one another in each case by means of insulation layers and are arranged in a plane-parallel manner, a compact low-inductive busbar arrangement can be obtained which has only three busbar planes. If, in a three-point phase module, not one semiconductor switch but two or three semiconductor switches are used for a respective switch, then it is possible to arrange additional busbars of the three-point phase module with a series connection number greater than one in at least one busbar plane. Consequently, the low-inductive busbar arrangement according to the present invention continues to have only three busbar planes, but the number of busbars within the busbar planes increases.
In one embodiment of the low-inductive busbar arrangement for a three-point phase module according to the present invention with the series connection number One, a load terminal busbar, a positive and a negative intermediate circuit terminal busbar are arranged in one busbar plane, a branch busbar is arranged in a next busbar plane and a neutral point terminal busbar is arranged in a further busbar plane. The arrangement of these three busbar planes relative to one another is arbitrary, an arrangement in which the busbar plane with the neutral point terminal busbar is used as an outer busbar plane being particularly advantageous.
If, for each switch of the three-point phase module, not one semiconductor switch but two or three semiconductor switches are used (series connection number Two or Three), then a three-point phase module of this type also additionally has connection busbars which are arranged in a busbar plane of the low-inductive busbar arrangement, the branch busbars advantageously being arranged in the busbar plane which already has the load terminal busbar and a positive and negative intermediate circuit terminal busbar. This division of the various busbars of a three-point phase module between three busbar planes means that the busbar arrangement can be adapted to the electrical construction of the phase module in a simple manner.
By way of example, if the semiconductor switches used are increased from two to three per switch of the three-point phase module, only six further connection busbars are required, which are additionally arranged in the corresponding busbar plane. Since, when the number of semiconductor switches per switch of the three-point phase module is increased, the spatial extent of this three-point phase module increases, there is enough space in the corresponding busbar plane for accommodating further connection busbars.
In a further advantageous embodiment of the low-inductive busbar arrangement for a three-point phase module, the neutral point terminal busbar is designed in such a way that this covers the busbars of the other two busbar planes. This configuration of the neutral point terminal busbar further reduces the value of the leakage inductance.
In a further advantageous embodiment of the low-inductive busbar arrangement for a three-point phase module, the neutral point terminal busbar is designed in such a way that the terminal lugs of the intermediate circuit terminal busbars are likewise covered. This embodiment of the neutral point terminal busbar reduces the value of the leakage inductance even further.
In a further advantageous embodiment of the low-inductive busbar arrangement, the three busbar planes are adhesively bonded to one another. A compact design is thus obtained for the busbar arrangement, with the result that the assembly outlay for a three-point phase module is considerably reduced and simplified. Moreover, the adhesive-bonding layers perform the function of insulation between adjacent busbar planes.
In a further advantageous embodiment of the low-inductive busbar arrangement for a three-point phase module, the connection busbars are configured uniformly. This means that the existing space of a busbar plane can be utilized optimally in terms of area. Moreover., the stock-keeping of the busbars and the assembly of the low-inductive busbar arrangement are simplified.
In a further advantageous embodiment of the low-inductive busbar arrangement for a three-point phase module, the connection busbars of the upper and lower bridge half, respectively, of the three-point phase module are spatially arranged in a row in each case, these being spatially arranged next to one another. This halves the length of the low-inductive busbar arrangement, which means, moreover, that the intermediate circuit terminal and the load terminal busbars can be arranged spatially oppositely in a busbar plane.
This configuration of a low-inductive busbar arrangement for a three-point phase module according to the present invention means that it is now possible to combine three such low-inductive busbar arrangements by means of a two-layer intermediate circuit busbar system to form a low-inductive busbar arrangement for a polyphase three-point power converter, without major outlay of time and expense.
In order to elucidate an exemplary embodiment of the present invention in further detail, reference is made to the drawings, which schematically illustrate a low-inductive busbar arrangement for a three-point phase module.